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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Effect of Repeated Exposure to Unpredictable Reward on Dopamine Neuroplasticity

Mathewson, Sarah Ann 15 February 2010 (has links)
Drugs of abuse elicit dopamine release unconditionally, sensitizing the reward system to drugs and drug-associated stimuli resulting in compulsive drug-seeking and drug-taking behaviour. It has been discovered that these same dopamine neurons consistently respond to natural rewards when the reward delivery is at maximum uncertainty (50%). Reward uncertainty is a defining feature of gambling. Therefore, chronic increases in dopamine release from gambling-like stimuli could lead to sensitization of the reward pathways and contribute to gambling pathology. This study investigated the effects of repeated exposure to different probabilities of sucrose reward (0, 25%, 50%, 75%, 100%) on sensitivity to an amphetamine challenge (0.5 mg/kg) and development of sensitization after multiple amphetamine doses (5 x 1.0/kg) in Sprague–Dawley and Lewis rats. No significant group differences were found during the amphetamine challenge or amphetamine sensitization in either strain. Opportunities for improvement in the experimental paradigm and for future research are discussed.
2

The Effect of Repeated Exposure to Unpredictable Reward on Dopamine Neuroplasticity

Mathewson, Sarah Ann 15 February 2010 (has links)
Drugs of abuse elicit dopamine release unconditionally, sensitizing the reward system to drugs and drug-associated stimuli resulting in compulsive drug-seeking and drug-taking behaviour. It has been discovered that these same dopamine neurons consistently respond to natural rewards when the reward delivery is at maximum uncertainty (50%). Reward uncertainty is a defining feature of gambling. Therefore, chronic increases in dopamine release from gambling-like stimuli could lead to sensitization of the reward pathways and contribute to gambling pathology. This study investigated the effects of repeated exposure to different probabilities of sucrose reward (0, 25%, 50%, 75%, 100%) on sensitivity to an amphetamine challenge (0.5 mg/kg) and development of sensitization after multiple amphetamine doses (5 x 1.0/kg) in Sprague–Dawley and Lewis rats. No significant group differences were found during the amphetamine challenge or amphetamine sensitization in either strain. Opportunities for improvement in the experimental paradigm and for future research are discussed.
3

Invertebrate life-history trade-offs and dispersal across a pond-permanence gradient

Galatowitsch, Mark Louis January 2014 (has links)
Flexible life-history traits and dispersal may allow generalist populations to persist across a range of habitats despite experiencing contrasting selection pressures. Invertebrates exploiting temporary ponds must develop quickly and disperse as adults, or have wide environmental tolerances. Conversely, permanent-pond invertebrates must avoid a suite of predators (e.g., fish and dragonflies). This gradient of pond permanence can result in life-history trade-offs that influence fitness, population dynamics, and genetic structure. In addition, recruitment between habitats may balance juvenile life-history trade-offs and be crucial to sustain generalist invertebrate populations in ponds with unpredictable hydrology. Through a multi-year survey of three pond complexes in the Canterbury high-country and a series of mesocosm experiments using two generalist pond invertebrates, Xanthocnemis zealandica damselflies and Sigara arguta waterboatmen, I found these two species had alternative life-history strategies that influenced their distributions across the pond-permanence gradient. With longer juvenile development, X. zealandica benefited from flexible life-history traits: temporary-pond X. zealandica had accelerated development and short-term desiccation tolerance, but were excluded from ponds with long dry periods, whereas, permanent-pond X. zealandica had extended development and predator avoidance behaviours (e.g., reduced movement and refuge-use). In contrast, S. arguta had an opportunistic life-history strategy with a fixed, rapid development response that allowed them to inhabit more temporary ponds, but they were intolerant of drying and limited to permanent ponds that contained shallow refuges from fish. These results illustrate how alternative life-history strategies enabled two generalist species to achieve broad realised niches. Recruitment between habitats also appeared to be important for balancing trade-offs and maintaining meta-populations across the pond-permanence gradient. To evaluate the importance of X. zealandica dispersal among and within pond complexes I used microsatellite analyses. While there was unique genetic population structure between the North and South Islands, at lower spatial scales there was little variability in genetic diversity and limited genetic structure in populations, likely due to gene flow among different habitat types. Overall, this work shows how an interaction of juvenile strategies and adult dispersal could reduce life-history trade-offs, resulting in weak selection pressures across an unpredictable disturbance gradient. Whether increasingly unpredictable hydrological patterns under climate-warming favour generalist species will likely depend on how well generalist life-history traits and dispersal allow exploitation of a range of habitat types and resilience to variable selection pressures. Higher mean summer rainfall in New Zealand may allow both species to exploit more temporary ponds, whereas longer dry periods between extreme precipitation events could limit X. zealandica distributions. Thus, species with generalist strategies are likely to be favoured under warming, but their specific life-history strategies will likely promote or limit their ability to exploit more unpredictable habitats.
4

BREED

Randestad, Stina January 2016 (has links)
Breed has a concept and a main goal, to be unpredictable and visually impressive. The idea that it was built on was to try to create a collection with the method of breeding and the rules of genetics. At first, twelve individuals were created. They were all given characteristics – “genes”, handed out in a random way, decided by the toss of a dice. The individuals bred and were blended into a second generation, who thereafter procreated into a third. This third generation of eight characters, four females and four males, carry genes and features from their ancestors. They have been twisted, mutated and mixed, just like in nature. It is voluminous line-up with clashes between references, colours and styles. The challenge has been to let chance take decisions and to do something that was unexpected and was going to give an unpredictable result. Breed has not been done for a commercial destination but would be suitable for styling artists, editorials for fashion magazines, costumes in music videos or artistic films. The method is supposed to make people interested, the result is supposed to give the onlooker a smaller chock, a tingling sensation and the impression of a new subculture, a modern day tribe or a new breed. Or simply “What crazy person made this?”
5

Designing emergent business process : the case of the foreign procurement process of Kuwait Ministry of Defence

Al-Sabah, Shamayel Ahmad Khaled January 2015 (has links)
Business processes can be divided into standardisable and non-standardisable processes. Such processes are characterised by their activities, events, states and time-points. The conditions in which process activities, events, states and time-points occur determines how they are observed, recorded and acted upon. Under predictable and stable conditions an observer can record them by predetermining them and this can be done using existing process design approaches and methodologies. Such processes are termed standardisable processes; for example a process for manufacturing cars. However, under unpredictable and unstable conditions an observer cannot record them by predetermining all the possible events, because uncertainty leads to unpredictable events occurring. Such processes are termed non-standardisable processes and in this thesis as emergent processes; for example special engineering projects like building the Channel Tunnel. Therefore, a new approach is required for designing non-standardisable processes. Process events are significant because the observer notices and records them. Significantly, the observer of events also has to act on them. Whether process events occur in predictable and stable conditions or unpredictable and unstable conditions, makes a difference to how an observer notices, records and acts on them. This is highly significant for this thesis argument, because as non-standardisable process events can be unexpected and unpredictable or emergent a new approach is required to design them. This thesis advances knowledge of designing non-standardisable processes by conceptualising them as emergent business processes (EBP) and contributing a new approach for designing them using action research and the deferred design approach as a process design methodology. Uncertain and unpredictable conditions is characterised here as emergence. The observer cannot predetermine all the possible process events for processes that operate in emergent conditions and cannot determine how to act upon unpredictable process events, because some events will be predictable and others unpredictable. The pragmatist research methodology was used to research to identify and resolve the problem with EBP in the Foreign Procurement Division (FPD) of the Kuwait Ministry of Defence. It was also used an approach for designing EBP. The research contributes the new understanding of non-standardisable processes as emergent business processes. This is a significant contribution because it is conceptualisation that is not found in the literature. This conceptualisation recognises the need to find new approaches for designing and implementing EBP. Therefore, the research also contributes a new approach for designing EBP using the action research methodology as a process design methodology.
6

Avaliação do papel modulador da oubaína no eixo hipotalâmico-pituitário-adrenal em ratos submetidos ao estresse crônico imprevisível. / Evaluation of the role of ouabain in the hypothalamic-pituitary-adrenal axis in rats submitted to unpredictable chronic stress.

Leite, Jacqueline Alves 05 December 2018 (has links)
A ouabaína (OUA), um inibidor da Na+ ,K+-ATPase, foi identificada como uma substância endógena presente no plasma humano, e parece estar envolvida na resposta ao estresse agudo, em animais e seres humanos. O estresse crônico é um importante fator agravante de doenças psiquiátricas, incluindo depressão e ansiedade. Além disso, problemas cognitivos são cada vez mais reconhecidos como importantes componentes da ansiedade e depressão. Diante disto, o presente trabalho buscou investigar os efeitos da OUA (1,8 <font face = \"symbol\">mg/kg) na hiperatividade do eixo HPA, na neuroinflamação, na expressão de receptores e proteínas envolvidos na plasticidade sináptica, nos efeitos comportamentais (como déficit de memória de longa duração, depressão e ansiedade) e atividade da Na+,K+-ATPase induzidos pelo protocolo de estresse crônico imprevisível (CUS) realizado ao longo de 14 dias em ratos. Nossos resultados demonstraram que o tratamento intermitente com OUA é capaz de reverter a hiperatividade do eixo HPA induzido pelo CUS, por meio da redução de glicocorticoide, redução na expressão de CRH-CRHR1, bem como diminuir a neuroinflamação, e aumentar os níveis de BDNF e fazer o que na expressão dos receptores CRHR2. Essas alterações bioquímicas contribuíram para uma reversão nos prejuízos na memória de longo prazo induzida pelo CUS. Ademais os animais tratados apenas com OUA, bem como os submetidos ao CUS e tratados com OUA obtiveram uma melhora na memória emocional, averiguada no teste comportamental de condicionamento da memória ao medo. Os resultados encontrados sugerem que o protocolo de CUS por 14 dias promove uma adaptação neuronal facilitando a redesignação da memória ao medo, aqui configurado pelo choque, e o tratamento com a OUA abrevia esse processo. Em conclusão os nossos resultados sugerem que o tratamento intermitente com OUA suscita uma adaptação no eixo HPA, por meio de alterações na expressão dos receptores para CRH no hipocampo e hipotálamo, resultando em uma adaptação na memória emocional relacionada ao medo. / Ouabain (OUA), an inhibitor of Na+, K+ -ATPase, has been identified as an endogenous substance present in human plasma, and appears to be involved in the response to acute stress in animals and humans. Chronic stress is an important aggravating factor of psychiatric illness, including depression and anxiety. In addition, cognitive problems are increasingly recognized as important components of anxiety and depression. The present work aimed to investigate the effects of OUA (1.8 <font face = \"symbol\">mg/kg) on HPA axis hyperactivity, neuroinflammation, expression of receptors and proteins involved in synaptic plasticity, behavioral effects (such as long-term memory deficit duration, depression and anxiety) and Na+,K+-ATPase activity induced by the unpredictable chronic stress protocol (CUS) performed over 14 days in rats. Our results demonstrated that intermittent treatment with OUA was able of reversing CUS-induced HPA axis hyperactivity, by reducing glucocorticoid levels, CRH-CRHR1 expression, as well as reducing CUS-induced low-grade neuroinflammation, and increase BDNF levels and expression of CRHR2 receptors. These biochemical changes contributed to a reversal in CUS-induced long-term memory impairment. In addition, animals treated only with OUA, as well as those submitted to CUS, and also treated with OUA obtained an improvement in emotional memory, which was explored in the fear conditioning test. These results suggest that the CUS protocol of 14 days promotes a neural adaptation facilitating a reassignment of the memory to the fear, here configured by the shock, and the treatment with the OUA shortens that process. In conclusion, our results suggest that intermittent treatment with OUA induces an adaptation on the HPA axis, through alterations in the expression of receptors for CRH in the hippocampus and hypothalamus, resulting in an adjustment in fear-related emotional memory.
7

Motor control of the knee : kinematic and EMG studies of healthy individuals and people with patellofemoral pain

Stensdotter, Ann-Katrin January 2005 (has links)
Patellofemoral pain (PFP) is believed to be associated with deficits in coordination between the different heads of the quadriceps muscle; however, considerable debate exists in the literature regarding the presence of such a deficit. Discrepancies between studies may be explained by differences in experimental tasks, such as whether the task is performed with open (OKC) or closed kinetic chain (CKC), or whether the activity is voluntary or triggered. Particular interest has been directed toward the function of the vastus medialis obliquus (VMO), which is a short muscle with limited ability to exert torque across the knee joint, but probably has a particular role in controlling patellofemoral joint position. Another short muscle that may influence knee joint position control is popliteus (POP), which is located in the back of the knee. This thesis investigates task specific activity of quadriceps in CKC versus OKC and studies the relative activity between the four heads of the quadriceps in PFP subjects compared to controls without knee pain in voluntary activity (CKC and OKC) and postural responses to balance perturbations. In addition, this thesis investigates the presumed function of POP for control of joint position in postural tasks in healthy individuals. All subjects were of normal weight and height and between 18 and 40 years. Quadriceps activity was tested for isometric with identical joint configuration in CKC and OKC, and it was performed as a reaction time task. Balance perturbations were elicited by unpredictable anterior and posterior translations of the support surface. Function of POP was investigated in unpredictable support surface translations and in self induced provocations to balance by moving the arms. Muscle activity was recorded with electromyography (EMG). Optic kinematic analysis was used to obtain specific movement responses to perturbations of balance. The quadriceps muscles were activated differently in CKC and OKC. VMO was activated earlier and to a greater degree in CKC. Rectus femoris was activated earlier and to a greater degree in OKC. PFP subjects reacted slower in both CKC and OKC, but there was no difference between groups in the relative activity between the different heads of the quadriceps. In the unpredictable support surface translation in the anterior direction, PFP subjects responded with earlier onset of VMO and with greater trunk and hip flexion in the anterior translation. POP activation in response to support surface translations in both directions occurred before all other muscles measured. In the self-initiated provocations of balance, POP was activated after the initiation of the balance provocation. This thesis concludes that quadriceps activity was task specific. The lack of difference between groups in OKC and CKC, and the difference between groups in postural responses suggest that variations in motor behaviour may occur only in tasks habitually performed. Differences in muscle activation patterns may be related to compensatory strategies to unload the quadriceps muscles and the patellofemoral joint. Furthermore, this thesis suggests that POP muscle may have a particular role in active control of the knee joint.
8

Besöksnäringens stabilitet och sårbarhet i Stockholms stad : En kvalitativ studie om Stockholms stads besöksnäring

Lazraq Byström, Adam January 2020 (has links)
The tourism sector in Stockholms city, Sweden, is a dynamic industry that through the years has generated large revenues and job openings. Unpredictable events such as terrorism, pandemics, natural disasters and climate changes, may have great imapct on the tourism sector. This may be true to most cities in the world including Stockholm. in this thesis, the effect of various unpredictable events has been investigated through interviews with city of Stockholm and the authority for community protection and preparedness. In use of strenghts, weaknesses, opportunities and threats (SWOT-analys). The main conclusion of this thesis is that the Covid-19 pandemic (year 2020) has shown that the emergency preparations for unpredictable events are incorrectly dimensiond. This means that the city of Stockholm needs to work more proactively in the future to ensure that the tourism sector is not jeopardized during upcoming unpredictable events.
9

Fältarbetets uppsökande natur - En kvalitativ studie om fältarbetares arbetssätt och eventuella svårigheter som uppstår

Hadzic, Ajsa, Bezzina, Samir January 2020 (has links)
The primary purpose of this thesis was to examine the work methods implemented by outreach workers in their interaction with at risk youths. The secondary purpose was to research the possible difficulties that may occur and the tactics to deal with these difficulties. In order to examine the purposes presented the authors produced a qualitative study with 5 semi-structured interviews with outreach workers. After conducting the interviews, the authors used thematization in order to illustrate the empirical data. The theoretical framework used to analyze the empirical data consist of three theories; the theory of communication, system theory and social bond theory. The results of the empirical material gathered from the interviews and from the analyzation of the interviews using out theoretical framework, provided multiple answers as it relates to the purpose. The results regarding the primary purpose showed that there is a lack of evidence-practice within the field of outreach work, which in turn leads to the fact that there is a vast variety of work methods applicable within their field. The results of interviews implied that outreach workers adapt their work methods depending on the situation and their personal expertise indicating that there are no specific set of methods that have to be used. As it pertains to the secondary purpose a clear correlation is shown between the vast variety of work methods and the many difficulties that may occur. Subsequently the occurrence of the different difficulties ensues based on the diverse established work methods. The study highlights the knowledge, communicational abilities and social skills of the individual outreach worker as way to reduce the probability of the conceivable diverse difficulties from occurring.
10

Creating Human-like AI Movement in Games Using Imitation Learning / Imitation Learning som verktyg för att skapa människolik rörelse för AI-karaktärer i spel

Renman, Casper January 2017 (has links)
The way characters move and behave in computer and video games are important factors in their believability, which has an impact on the player’s experience. This project explores Imitation Learning using limited amounts of data as an approach to creating human-like AI behaviour in games, and through a user study investigates what factors determine if a character is human-like, when observed through the characters first-person perspective. The idea is to create or shape AI behaviour by recording one's own actions. The implemented framework uses a Nearest Neighbour algorithm with a KD-tree as the policy which maps a state to an action. Results showed that the chosen approach was able to create human-like AI behaviour while respecting the performance constraints of a modern 3D game. / Sättet karaktärer rör sig och beter sig på i dator- och tvspel är viktiga faktoreri deras trovärdighet, som i sin tur har en inverkan på spelarens upplevelse. Det här projektet utforskar Imitation Learning med begränsad mängd data som etttillvägagångssätt för att skapa människolik rörelse för AI-karaktärer i spel, ochutforskar genom en användarstudie vilka faktorer som avgör om en karaktärär människolik, när karaktären observeras genom dess förstapersonsperspektiv. Iden är att skapa eller forma AI-beteende genom att spela in sina egna handlingar. Det implementerade ramverket använder en Nearest Neighbour-algoritmmed ett KD-tree som den policy som kopplar ett tillstånd till en handling. Resultatenvisade att det valda tillvägagångssättet lyckades skapa människolikt AI-beteende samtidigt som det respekterar beräkningskomplexitetsrestriktionersom ett modernt 3D-spel har.

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